Good news (I hope): I smeared some of the EnerCal on her paw and put some beef cat food over it. She completely ignored it and went to sleep. An hour later, I heard a slight licking/smacking noise, and came in to see her paw without the food on it and what looked like the last second of her licking the "blanket" (tshirt) she was on. I started petting her as soon as I noticed this, her purr came back for the first time in about 24 hours, and she went back to sleep. I have to think this is a really good sign.